Primary function of leaf

Primary function of leaves: 

1. Photosynthesis: The principal function of the leaves is to manufacture organic food. The seat of photosynthesis are the green cells of leaf having chlorophyll.
2. Transpiration: The loss of water from leaf surface is known as transpiration. It is necessary to create force or tension in water column and thus cause ascent of sap.
3. Gaseous exchanges: It takes place in leaves through stomata during the process of photosynthesis and respiration.

Secondary function of leaf

   Secondary functions of leaves:

1. Storage of food in leaf bases e.g. onion.
2. Water is stored in the leaves of succulent nature (Bryophyllum and Aloe).
3. Protect the plants from grazing animals when modified into spines (Opuntia and Barberry).
4. It reduces the rate of transpiration when changed into phyllode e.g. Acacia auriculiformis.
5.  They help in climbing the plants having weak stem, when modified into tendrils and hooks.
6. Leaves help the plants in vegetative multiplication (Bryophyllum).
7. Leaves act as balancers for floating when modified into roots e.g. Salvinia.
8. The leaves are modified into sepals, petals, stamens and carpels to take part in sexual reproduction.